In recent years, the use of wireless communication systems having mobile transceivers which communicate with a hardwired network, such as a local area network (LAN) or a wide area network (WAN), has become widespread. The mobile transceivers, commonly referred to as mobile terminals, may take one of several different forms. For instance, in retail stores hand-held scanning units may be used to allow for scanning inventory bar codes. In a warehouse, portable units mounted to a vehicle may be used to gather information from the warehouse floor. In a medical environment, the mobile terminal may take the form of a pen based workslate which allows medical personnel to work with full page screens.
In a typical wireless communication system, each mobile terminal communicates with a networked system via a radio or optical link in order to allow for a real time exchange of information. The mobile terminals communicate through one of several base stations interconnected to the network. The base stations allow for a wireless data communication path to be formed. Consequently, such mobile terminals significantly facilitate worker efficiency since data can be gathered, transmitted and even processed at a remote site in real time.
However, despite the aforementioned advantages associated with mobile terminals, there is a strong need for a more ergonomic mobile terminal. For example, with the widespread use of computers, portable digital assistants, and the like there is an ongoing struggle to enhance display systems to allow for user friendly viewing of information on the screen. One standard feature available on many electronic devices to accommodate user friendly viewing is a contrast control. The contrast control allows a viewer to lighten or darken the display screen to adjust for current ambient lighting conditions. For instance, on particularly sunny days a viewer of a display screen may choose to darken the screen to allow for easier readability. Alternatively, as the day gets darker the viewer may choose to lighten the screen.
Furthermore, many such mobile terminals have liquid crystal displays (LCDs) and as they are moved from one point to another the LCD may be exposed to temperature variances which affect the LCD contrast. For example, extreme cold renders the liquid crystal material opaque and extreme heat renders the material transparent. Consequently, some form of contrast control is required to compensate for the effects of temperature variances on the liquid crystal display.
To adjust the contrast control, manufacturers of electronic devices (including mobile terminals) typically include two easily accessible contrast control buttons. One of the contrast control buttons would be used for darkening the screen and another of the contrast control buttons would be used to lighten the screen. As opposed to using buttons, there have also been electronic devices made with rotatable knobs and sliding controls which provide for similar functionality. For instance, by either turning or sliding such a control, the contrast on the screen would adjust appropriately.
One area of growing popularity in the computer industry is the use of wireless pen based computer systems. Such computers are used by workers in warehouses and on manufacturing floors as well as outdoors by postal workers, utility servicemen, etc. Given the environment in which such mobile terminals are often utilized, it is not beneficial to provide a contrast control feature which uses rotatable or sliding controls since such controls are prone to breaking and often provide an inlet where rain or other moisture is able to seep into the computer and damage internal wiring. Buttons are more durable and easier to secure from moisture, however, since two buttons are needed this often takes up a significant portion of valuable space on the mobile terminals control panel. This is especially true of mobile terminals built for ruggidized outdoor activity since each button on the portable computer is oversized and spaced apart to allow for easy management by individuals who may be wearing gloves or the like.
The portability of these computing devices places demands on reduction of size. In order to meet this demand, it is desired to optimize the key board arrangement of such devices so as to optimize space. A single button switch is known in the art for bi-directionally controlling volume. However, there are deficiencies associated with this conventional switch. In particular, the switch must be continuously depressed in order to increase or decrease the volume. Once the button is released, the volume direction is changed so that the next time the button is pushed the volume moves in the opposite direction. A problem with such a design is overshoot and undershoot of a desired function level. For example, if a user desires to increase the volume he/she must keep the button depressed. If the button is pressed too long, the volume is set to be excessively louder than desired. If the button is not pressed down long enough the volume is too low. In the case where the button is not pressed down long enough, the next time the user pushes down the button the volume is further reduced. Consequently, fine tuning of the volume is not achieved as easily as if two buttons were available (one for each direction of change in volume).
Thus, in light of the above, there is a strong need for a single button switch which can accomplish substantially the same amount of functions that can be accomplished conventionally with two switches and avoid the problems associated with conventional single button switches. In particular, there is a need in the art for a contrast control feature which does not have the limitations described above. More specifically, there is a need for a single button contrast control feature which is durable, easy to seal, requires a minimum amount of space, and affords for fine tuning a function easily.